Projections of stronger and longer-lasting marine heatwaves underscore the emerging need for formalised marine heatwave response plans to guide response actions at all stages of these extreme events. Four key components of a globally applicable marine heatwave response plan for ecosystems and fisheries are presented, including an early warning system, a response level assessment, response actions and a communication strategy. Monitoring resources and methods, response actions and communication options that support each of these components are described through case-study applications of marine heatwave response plans developed for New South Wales, Australia. These novel marine heatwave response plans, along with insights gained through their development and application, contribute to capacity being developed by researchers and managers across numerous jurisdictions facing the emerging need to respond to climate-driven environmental extremes.